1. Field of the Invention:
The present invention relates to a layered-type manganese dry battery. More particularly, it relates to a conductive carbon coat, the surface of which is physically treated, the said conductive carbon coat constituting a zinc-carbon bonded electrode (hereinafter referred to as the "bonded electrode") used in a layered manganese dry battery, and to a layered-type manganese dry battery using the bonded electrode.
2. Description of the Prior Art:
Generally, a layered-type manganese dry battery, which is typified by the 6F22 type, has a structure as shown in FIG. 1, in which six unit cells 7 with a positive current collector plate 5 stacked on top of them are held together, coated with wax, and covered with a PVC tube 4, the contents thus contained in the PVC tube 4 being temporarily clamped in an outer can 10 with a terminal plate 3 and a bottom plate 9 disposed at the top and bottom, respectively. A positive electrode lead plate 6 is disposed on the positive current collector plate 5, and a negative electrode lead plate 8 is disposed at the bottom of the six unit cells 7. A positive electrode terminal 1 and a negative electrode terminal 2 are disposed on the terminal plate 3.
Each unit cell 7 comprises, as shown in FIG. 2, a bonded electrode 14 made of a conductive carbon coat 15 integrally bonded to a zinc plate 16, a positive electrode composition 11, and a separator 13, which separates the bonded electrode 14 from the positive electrode composition 11, all of these being contained in a cell grommet of a PVC tube 12.
The bonded electrode of a conventional layered-type manganese dry battery has the structure shown in FIG. 6, which is composed of a conductive carbon coat 15 and a zinc plate 16. The conventional bonded electrode is manufactured by either applying a conductive carbon paint to form a conductive carbon coat 15 on one side of the zinc plate 16 that serves as the negative electrode, or by press-fitting the conductive carbon coat 15 onto the zinc plate 16. In the latter case, a flexible sheet-like material, which is made of a synthetic resin and a large quantity of carbon powder mixed together into a paste and rolled into a thin film by a press roller, has been used as the conductive carbon coat 15. The thus formed conductive carbon coat 15 has a smooth surface like that of a reduction roll rolled into a sheet-like form by the heat press roller.
The conventional bonded electrode with the above-mentioned structure has the following problem when the zinc sheet that has been bonded to the conductive carbon coat is punched into a prescribed shape by a press. That is, when a chute is installed below the die of the press in order to enhance the work efficiency in transporting the bonded electrodes from the press to the next process, if the bonded electrodes are continuously fed through the chute by the pressure of the press so that the bonded electrodes are aligned properly in the chute with their top and bottom surfaces facing the respectively specified sides, the bonded electrodes will become firmly pressed together and stick to each other via the soft conductive carbon coat, thus causing the problem that they do not separate from each other when delivered to the next process.
To avoid this problem, the previous method to prevent the electrodes from sticking to each other was by attaching paper to the surface of the zinc plate or to avoid application of pressure by punching the electrodes one by one without using a chute.
Moreover, the layered-type manganese dry battery has such a structure that more than one unit cell of the same type is stacked one above another to obtain a high output voltage. In such a battery, it is required to reduce the contact resistance between the unit cells and to maintain the low contact resistance not only during discharge but also when the battery is out of use and stored on a shelf. It is also required, particularly under a high load discharge condition, that the conductive carbon coat has the largest possible conductivity and current collecting property within a limited contact area.